Infrared heater



Aug. 31, 1965 D. w. HARTZELL ETAL 3,203,413

INFRARED HEATER Filed Aug. 24, 1961 INVENTORS'. pal/440 VL #4272!!!ART/#7? 5 1 005 United States Patent 3,203,413 INFRARED HEATER Donald W.Hartzell and Arthur E. Yoos, Centralia, lll., assignors to Lear Seigler,Inc., a corporation of Delaware Filed Aug. 24, 1961, Ser. No. 133,642

4 Claims. (Cl. 126-92) This invention relates to a gas heater andparticularly to a gas infrared heater.

As is generally known, space heating by means of infrared radiationsoflfers'in certain installations advantages not attainable through theuse of conventional heaters that rely principally upon convection. Dueto absorption of infrared radiations by the human body, both generalthermal comfort and therapeutic benefits can be effectively attainedthrough infrared heating. Residential bathroom installations offer oneexample where infrared heating is particularly applicable.

' In a gas infrared heater, it is required that a surface of a burnerelement be heated to incandescence to serve as a high temperature sourceof radiant heat. Various burner elements of refractory materials havebeen developed in which combustion of a fuel mixture occurs near onesurface of the element so that such surface is heated to the temperaturerequired to provide infrared radiations. While the range of wave lengthsin the infrared band is relatively wide, the wave length of the infraredradiations presently preferred for thermal comfort is between 2.5microns and 3.5 microns. These wave lengths provide the penetratingquality which produces an optimum degree of body warmth. Wave lengths inthe desired range from 2.5 to 3.5 microns are emitted where the heatedbody is at a temperature of from 155 0 to 1600 F.

The present invention is a gas infrared heater including a burnerelement having a plurality of passages extending through it from aninner surface to an outer surface. Means are provided for maintaining acombustible fuel mixture of primary air and gas against the innersurface of the burner element to force the fuel mixture through thepassages to be burned near the outer surface. Means are provided forconducting secondary air to the burner element. Flow-directing means arespaced apart from the outer surface of the burner element to cause thesecondary air to pass across the outer surface of the burner element.

A particular feature of the gas infrared heater of the present inventionlies in the flow-directing means disposed in a spaced apart relationshipwith respect to the outer surface of the burner element, theflow-directing means being of a material such that infrared radiationsreadily pass through it. It is the outer surface of the burner elementwhich is heated to the temperature required for infrared radiations. Ithas been found that the provision of the flow-directing means to causeflow of secondary air across the outer surface results in improved andmore constant combustion at the outer surface. As a consequence,constant radiation of infrared emissions of desired wave lengths isobtained. It is possible thereby to maintain the temperature of theouter surface of the burner element between 1550 and 1600 F. so that theinfrared emissions have a wave length in the range most beneficial forthermal comfort. These operating charac- 3,203,413 Patented Aug. 31,1965 teristics are obtainable at a gas manifold pressure of 3.5" H 0,the pressure at which gas is normally supplied to residences.

In the gas infrared heater of the present invention, the capacity of agiven burner element, in terms of output in B.t.u.s, is increased byapproximately one-third as compared to a gas infrared heater in which noflow-directing means for causing flow of secondary air across the burnerelement is provided. While it is not intended to limit the apparatus ofthe present invention to a particular theory of operation, it is thoughtthat this unexpected increase in capacity is the result of more completecombustion produced by the continuous removal of combustion productsfrom the surface of the burner element by the flow of secondary airacross such surface.

An added advantage of the gas infrared heater of the present inventionis that constant radiation of desired infrared emissions is obtainedeven in environments in which drafts cause variations in the radiationsof prior art infrared heaters. This characteristic makes the infraredheater of the present invention useful in warehouses, shops and the likewhere air currents can seriously impair the utility of prior artheaters.

The structure of the gas infrared heater of the present invention andthe manner of its operation will be more fully understood from thefollowing description made in conjunction with the accompanying drawingshowing a sectional elevation of one embodiment of the heater.

With reference to the drawing, a vented wall-mounted infrared heaterparticularly adapted for a residential vided by an aperture 22 locatedin a horizontal wall of the housing directly above the vertical wallwithin which the primary air intake is positioned. A grill 24 is fittedwithin aperture 22. This embodiment of the heater demonstrates thepresently preferred practice whereby both primary air and secondary airare derived from the same source so that both are initially at the sametemperature and pressure.

A burner assembly, generally indicated by 26, is supported within thehousing. cludes a cast iron burner body 28 defining an enclosed chamber30. A fuel mixture distributor 32 in the form of a tubular member issealably fitted through the bottom of the burner body so that its lowerend is located externally of the burner body and its upper end is Withinchamber 30. A semicylindrical section of the portion of the distributorwithin chamber 30 is removed to provide a fuel mixture outlet 34. Anadapter 36 is fitted to the lower end of the fuel mixture distributor.The adapter has air inlet openings in each of its four sides, three ofthe air inlet openings being shown and identified by reference character38. An orifice 40 is fitted in the bottom of the adapter and extendswithin it so that it is centrally positioned with respect to air inletopenings 38. A gas pipe 42 is joined to the orifice at one end and isconnected at its other end (not shown) to a source of fuel gas.

The burner assembly in- One wall of the burner body 28 is inclined at anangle of 45 and includes an opening 44. One or more ceramic burnerelements 46 are mounted within opening 44. While various burner elementsof refractory materials suitable for providing infrared radiations maybe used within the scope of the invention, it is presently preferredthat burner elements of the type described in US. Patent No.2,775,294issued December 25, 1956, be used. These elements include a plurality ofpassage 48 extending from the inher surface 50 of the burner element tothe outer surface 52 of the burner element. These elements incorporate aheat-retarding medium to reduce the thermal conductivity of the burnerelement so that the temperature at the inner surface is less thanone-fourth of the temperature of from l550 to 1600 F. at which the outersurface is maintained during combustion. The housing and hood are joinedto frame the burner element so that its outer surface is exposed to thespace in which the heater is mounted. A pilot light 54, suitablyconnected to a source of gas, is positioned adjacent outer surface 52 ofthe burner element. The pilot light shown in the drawing is a schematicrepresentation of a commercially available unit and includes athermocouple disc 54a dispossed above a lower disc 54b which is rovidedwith a circularly disposed array of gas jets.

A flow-directing member 56 is supported along its periphery by thehousing and is positioned in spaced-apart relationship with respect tothe outer surface of the burner element. The flow-directing member issubstantially coextensive with the burner element in size. In thepresently preferred form, the flow-directing member is mounted so thatit diverges slightly from the outer surface of the burner element, thelower end of the flow-directing memher being approximately /2 from theouter surface, and the upper end of the flow-directing member beingapproximately from the outer surface. The flow-directing member can alsobe in a parallel spaced-apart relationship with the outer surface of theburner element. Variations in the spaced-apart distance between theflow-directing member and the outer surface of the burner element can bemade to produce differeing chimney effects without affecting the basicfunction of the flow-directing member.

It is essential that the flow-directing member be of a material suchthat infrared radiations pass through it without substantial absorptionof the radiations. In the embodiment shown in the drawing, theflow-directing member is formed from a screen of l8-gauge wire havingmeshes to each inch. Such a screen is satisfactory in that it transmitsinfrared radiations while functioning to cause secondary air to flowacross the outer surface of the burner element, as will be hereinafterdescribed. In addition, however, other materials, such as, for example,a quartz glass or mica, each of which is capable of transmittingsubstantially all of the infrared radiations, can be used as theflow-directing member.

A reflector 58 made of highly polished steel is positioned near thelower end of the flow-directing member and is supported by a portion ofhood 16. A duct 60 is formed within the housing and is internally fittedto the hood member near the upper end of the flow-directing member toprovide a conduit 62 for flow of combustion products. The duct leads toan exhaust 64 which passes through the housing and is connected to avent 66 in the wall of the residence. Vent 66 is connected so as todischarge gases externally of the residence.

In operation, flow of gas is initiated through line 42 upon opening of asuitable flow control valve. While not shown, a knob or handle foropening and closing such a valve is mounted on the housing of theheater. Flow of gas through orifice 40 pulls primary air, in accordancewith well-known principles, through grill and air inlet openings 38 intothe adapter to form a combustible mixture of gas and air. The mixture ofgas and air flows through distributor 32 and is discharged into chamberthrough fuel mixture outlet 34. The combustible mixture of gas and airis maintained against the inner surface of burner element 46 so that theexisting pressure differential causes the combustible fuel mixture toflow through passages 48 of the burner element. Combustion of the fuelmixture occurs within these passages near outer surface 52 of the burnerelement.

Hot combustion products tend to rise in the space between outer surface52 and flow-directing member 56 and pass into duct 62. Secondary airenters the infrared burner of the present invention through grill 24 andrises to the lower end of the burner element. The flow-directing member56 causes the secondary air to flow across the outer surface of theburner element and pass into duct 62 together with the combustionproducts. The flow of secondary air across the outer surface of theburner element in the space between the outer surface and flow-directingmember 56 purges that region of combustion products. The improvedcombustion and constant radiation previously described are therebyattained. The outer surface of the burner element can be readilymaintained at a temperature of between l550 land 1600 F. so thatinfrared radiation having the wave lengths most beneficial for thermalcomfort are produced.

The arrangment for fiow of secondary air across the outer surface of theburner as herein described is inherently balanced with respect tomanifold pressure variations of the gas passing through orifice 40. Adecrease in pressure with resulting reduction in the amount ofcombustion products produces a decreased chimney effect so that lesssecondary air is drawn across the outer face of the burner element.

In the embodiment shown in the drawing, the ceramic burner elements arepositioned at an angle of so that the infrared radiations are directeddownwardly to provide full body warmth. It will be understood that theburner elements may also be placed in other positions without affectingthe basic operating characteristics of the heater. For example, theheater may be arranged as a ceilingrnounted unit in which the burnerelements are parallel to the ceiling. Variations of this nature in thestructure of the heater are within the scope of the present inventionand derive, together with the embodiment described, the advantages ofinstantaneous response and low service costs intrinsic in gas heaters,as Well as the improved and constant radiation resulting from thestructure of the infrared heater of the present invention.

We claim:

1. A gas infrared heater comprising a housing defining an enclosure, aburner element having a plurality of passages extending therethroughfrom an inner surface to an outer surface, means mounting the burnerelement in the housing so that the outer surface of the burner elementis inclined to have a vertical component, means for maintaining acombustible mixture of primary air and gas against the inner surface ofthe burner element for flow of the mixture through the plurality ofpassages and for combustion of the mixture near the outer surface,intake means spaced below the burner element for intaking secondary air,vent means spaced above the burner element, means capable oftransmitting infrared radiations adjacent the outer surface of theburner element and spaced therefrom to promote flow of secondary airacross the entire outer surface in close contact with said surface, thelower and upper ends of the outer surface of the burner element beingspaced from opposing ends of the infrared transmitting means to provideapertures for entry and exit of secondary air, first passage meansenabling flow of secondary air between the intake means and thesecondary air entry aperture, and second passage means enabling flowfrom the secondary air exit to the vent means.

2. Heater in accordance with claim 1 wherein an opposed end of the meanscapable of transmitting infrared radiations is spaced from the upper endof the outer surface of the burner element a greater distance than the 56 other opposed end of said means is spaced from the lower 1,738,33512/29 Thompson 126-92 end of the outer surface of the burner element.2,517,071 8/50 Wyatt 12692 3. Heater in accordance with claim 1 in whichthe 2,936,751 5/60 Forniti 126-92 25:1; capable of transmitting infraredradiations is a 5 FOREIGN PATENTS 4. Heater in accordance With claim 1in which the 535,753 2/ 55 Belgium means capable of transmittinginfrared radiations is spaced 416,474 9/34 Great from about one-halfinch to about three-quarters of an 744,980 2/56 l f inch from the outersurface of the burner element. 798,798 7/ 58 Gl'eat Bumm- RefierencesCited by the Examiner 10 JAMES W. WESTHAVER, Primary Examiner.

UNITED STATES PATENTS FREDERICK L. MATTESON, JR., FREDERICK KET-1,647,995 11/27 Humphrey 126-92 TERER Examine-

1. A GAS INFRARED HEATER COMPRISING A HOUSING DEFINING AN ENCLOSURE, ABURNER ELEMENT HAVING A PLURALITY OF PASSAGES EXTENDING THERETHROUGHFROM AN INNER SURFACE TO AN OUTER SURFACE, MEANS MOUNTING THE BURNERELEMENT IN THE HOUSING SO THAT THE OUTER SURFACE OF THE BURNER ELEMENTIS INCLINED TO HAVE A VERTICAL COMPONENT, MEANS FOR MAINTAINING ACOMBUSTIBLE MIXTURE OF PRIMARY AIR AND GAS AGAINST THE INNER SURFACE OFTHE BURNER ELEMENT FOR FLOW OF THE MIXTURE THROUGH THE PLURALITY OFPASSAGES AND FOR COMBUSTION OF THE MIXTURE NEAR THE OUTER SURFACE,INTAKE MEANS SPACED BELOW THE BURNER ELEMENT FOR INTAKING SECONDARY AIR,VENT MEANS SPACED ABOVE THE BURNER ELEMENT, MEANS CAPABLE OFTRANSMITTING INFRARED RADIATIONS ADJACENT THE OUTER SURFACE OF THEBURNER ELEMENT AND SPACED THEREFROM TO PROMOTE FLOW OF SECONDARY AIRACROSS THE ENTIRE OUTER SURFACE IN CLOSE CONTACT WITH SAID SURFACE, THELOWER AND UPPER ENDS OF THE OUTER SURFACE OF THE BURNER ELEMENT BEINGSPACED FROM OPPOSING ENDS OF THE INFRARED TRANSMITTING MEANS TO PROVIDEAPERTURES FOR ENTRY AND EXIT OF SECONDARY AIR, FIRST PASSAGE MEANSENABLING FLOW OF SECONDARY AIR BETWEEN THE INTAKE MEANS AND THESECONDARY AIR ENTRY APERTURE, AND SECOND PASSAGE MEANS ENABLING FLOWFROM THE SECONDARY AIR EXIT TO THE VENT MEANS.